· Blue-tailed Fire-bellied Newt

A two-tailed test is both, upper and lower tailed!

it is fuuton:rasenshirunken[wind element:sprailing shirunken]

UPDATE:

The strongest Rasengan is actually the massive rasenshuriken, or maybe tailed beast ball since they classify rasengan to be developed from the tailed beast ball ( manga spoiler).

no only one-tailed shukaku, two tailed cat three tailed turtle 8 tailed ox-cepholpod and the nine tailed fox (naruto)

The choice of one-tailed or two-tailed tests follows the logic of the hypothesis that is being tested! The one-tailed test, if appropriate, will be more powerful.